Development builds of courier, sqwebmail, and maildrop packages

Build 20130829 adds a small additional fix, which broke the maildrop's
xfilter command.

Changes:

• Major update to maildrop, adding the ability to search MIME-encoded
content. Search patterns must now be specified in the UTF-8 codeset
exclusively.

• To make room for the new MIME-aware maildrop, certain, and likely obsolete
mail server interfaces (mail handed to maildrop with an mbox-style From_
line, or with leading spurious blank lines) are no longer directly
supported; must use maildrop together with reformail. See the maildrop(1)
man page for more information.

• Update sqwebmail to write maildrop mail filters in UTF-8. It's unlikely
that any existing sqwebmail-written mail filters will have any non-Latin
search strings; but if they do, the rules will have to be rewritten.